MXPA03009094A

MXPA03009094A - Method for producing almn strips or sheets.

Info

Publication number: MXPA03009094A
Application number: MXPA03009094A
Authority: MX
Inventors: Mrotzek Manfred
Original assignee: Hydro Aluminium Deutschland
Priority date: 2001-04-04
Filing date: 2002-03-28
Publication date: 2004-11-22
Also published as: DE10116636C2; US20030042290A1; HU224554B1; KR20020077831A; US6743396B2; HU0201137D0; BR0201086B1; CA2380162A1; JP2004521190A; NO20034401D0; PL353152A1; CN1505692A; ZA200307721B; CN1252308C; HUP0201137A2; EP1247873B1; CZ298104B6; DE10116636A1; NO336134B1; WO2002083967A1

Abstract

The invention relates to a method for producing AlMn strips or sheets for, in turn, producing parts by soldering. According to the inventive method, input stock is produced from a melt, which contains (in wt. %) Si: 0.3 1.2 %, Fe: <= 0.5 %, Cu: <= 0.1 %, Mn: 1.0 1.8 %, Mg: <= 0.3 %, Cr + Zr: 0.05 0.4 %, Zn: <= 0.1 %, Ti: <= 0.1 %, Sn: <= 0.15 % and unavoidable companion elements, whose individual contents equal a maximum of 0.05 % while their sum totals a maximum of 0.15 %, and the remainder of the melt consists of aluminum. The input stock is preheated at a preheating temperature of less than 520 degree C during a holding time of no longer than 12 hours. The preheated input stock is then hot-rolled into a hot-rolled strip with a hot-rolling final temperature of at least 250 degree C, and the hot-rolled strip is cold-rolled into a cold-rolled strip without intermediate annealing. The inventive method makes it possible to economically produce aluminum sheets that, even after soldering, have a high level of strength, particularly a high yield point and an excellent resistance to corrosion.

Description

METHOD TO PRODUCE STRIPS OR LEAVES OF ALMN Description of the Invention The present invention relates to a method for producing AlMn strips or sheets, with which, in turn, components can be produced by welding. For example, heat exchangers for motor vehicles that are commonly produced from aluminum sheets, in which the components are individually pre-manufactured from heat exchangers, such as plates, tubes and manifolds, are linked together by welding. Therefore, the efforts that act, during the practical use, on the components produced in this way that are installed in the automobiles are significant, due to the sudden changes of temperature, to the vibrations of longer duration, to the effect of corrosion and similar issues. In particular, this applies to the plates, by means of which heat dissipation occurs. Defects in these heat exchange components that occur as a consequence of the inadequate properties of the aluminum material can lead to significant damage. In this context, those regions of the components referred to in the changes of the microstructure are presented due to the heat generated during the REF process. 150704 welding, changes that have been shown to be particularly problematic in the past. Due to the reasons described above, in addition to a good welding convenience, a high strength, and in particular, a high elastic limit Rpo.2, and a toughness even after the welding of the aluminum sheets of the type are required. which is under discussion. The aluminum sheets referred to must have, at the same time, a good degree of deformation and a high resistance to corrosion. A material for producing plates for heat exchangers is known from WO 97/18946, which contains (in percentage by weight) 0.2 to 0.5% Fe, 0.7 to 1.2% Si, 1.2 to 1.6% of Mn, 0.3% of Gg, 0.05% of Cu, 0.2% of Zn, 0.1% of Ti, and the unavoidable accompanying elements whose individual quantities are at more than 0.05% and whose sum is at more than 0.15%, as well as Also, it contains aluminum as the remnant. Ingots are cast from this material as a precursor material, which are subsequently preheated to an initial laminate temperature of at least 520 ° C and then hot rolled. The cold rolling process up to the final thickness that follows, is carried out in at least two stages, with an intermediate annealing step that has to be carried out for two hours at an annealing temperature that is between 360 and 400 ° C between the cold rolling stages.

It has been shown in the practical tests of the material produced according to the known method that the material properties of the aluminum sheets produced according to the related technique for specific applications are insufficient. In particular, this applies to the resistance and resistance to corrosion that still exists after the welding process in the region of the weld joints. Furthermore, it has been shown, for example, during the production of heat exchangers that the possibilities for the combination of components produced from the material known from WO 97/18946 with heat exchange components produced from another material of heat are restricted. light metal because the difference in corrosion potentials is too low. The objective of the present invention, based on the related technique described above, is to point out a method that uses aluminum sheets that can be produced in an effective cost mode, which even after being welded, have reliably high strength , in particular, a high elastic limit, as well as an outstanding corrosion resistance. The objective is achieved by a method for the production of Al sheets, with which components are produced in turn through the welding process, - in which a precursor material is produced from a fusion containing (in percentage by weight) 0.3 to 1.2% Si, 0.5% Fe , 0.1% Cu, 1.0 to 1.8% Mn, 0.3% Mg, 0.05 to 0.4% Cr + Zr, 0.1% Zn, 0.1% Ti, 0.15% Sn and unavoidable companion elements whose individual amounts are at more than 0.05% and whose sum is at most 0.15%, as well as, contains aluminum as the remainder, - in which the precursor material is preheated to a preheat temperature of less than 520 ° C with respect to a drying time of more than 12 hours, in which the preheated precursor material is hot-rolled on a hot-rolled strip, in which the hot-rolled strip is cold-rolled on a cold-rolled strip without a treatment of intermediate annealing, and - in which the cold rolled strip is finally subjected to a annealing The present invention is based on a composition of the melt which is used to produce the precursor material whose alloy contents are tailored to one another, in such a way that the danger of intercrystalline corrosion is reduced to a minimum and the corrosive attack because the sting is distributed uniformly on the surface. As a consequence, high corrosion resistance is guaranteed.

The alloy used according to the present invention and the parameters of the method for its processing are optimized, simultaneously, in such a way that an aluminum sheet, which has a good degree of deformation and high strength, in addition to values particularly high elastic limit Rpo.2, and a good elongation to the fracture, even after welding process, can be produced from it in a simple way in a hot rolling temperature that is placed in the medium temperature range, without the need for an intermediate annealing treatment during the cold rolled process. It has been determined, in the sheets produced according to the present invention, that the elastic limit Rpo.2 is at least 60 MPa after the welding process. In many cases, an elasticity limit Rp0.2 / at least 65 MPa could be established. The corrosion potential was regularly lower than -750 mV, in many cases even, it was lower than -800 mV (measured against GKE in accordance with ASTM G69). The silicon content also has a positive influence on the strength of the sheet after welding on the sheets of AlMn produced according to the present invention. However, it has been shown that silicon influences, simultaneously, the occurrence of intercrystalline corrosion in interaction with tin. Therefore, in the alloy used according to the present invention, the predetermined range for the silicon content is selected in relation to the content of tin, in such a way that an optimized conposition can be achieved with respect to the prevention of intercrystalline corrosion. . This guarantees a good corrosion resistance of the AlMn sheet produced according to the present invention and also a high strength at the same time. In particular, the latter would apply if the ratio of tin content [% Sn] in the silicon content [Si%] of the melt was 0.03, with the interaction of silicon and tin content with the ability to be optimized, in addition if the ratio of [% of Sn] / [% of Si] could be adjusted to 0.1. The addition of tin by the alloy in the indicated ratio is necessary, at least, when the Si content of the melt f was at least 0.75 percent by weight. However, the addition of tin in the indicated ratios would be advisable even in Si contents of 0.5 percentage by weight and higher. If the upper limit of the predetermined interval for the content of Si were restricted to at most 1.0 percent by weight, the aluminum sheets in which they were present, on the one hand, a high optimized resistance and, on the other hand, a minimized danger of intercrystalline corrosion, could be particularly produced reliably in the mode according to the present invention.

Iron stimulates the formation of primary phases in which silicon binds. Therefore, according to the present invention, the iron content is limited to at most 0.5 percent by weight. Through this limitation of the iron content, under the conditions of manufacture according to the present invention, it is guaranteed that the silicon is kept in solution. This could be particularly assured, reliably, if the iron content were limited to at most 0.3 percentage by weight. The copper content is limited to at most 0.1 percent by weight, preferably 0.05 percent by weight, in the alloy used in accordance with the present invention. Copper does not increase resistance, but also leads to a positive corrosion potential. However, a positive corrosion potential restricts the possibilities of combination with other materials. In addition, the corrosion behavior, in particular with respect to intercrystalline corrosion, worsens with the increase in Cu content. The Mn content of the merger, which is provided according to the present invention from at least 1.0 to more than 1.8 percent by weight, supports the strength of the sheet according to the present invention. Optimized strength values could be achieved reliably if the Mn content of the melt were at least 1.3 percent by weight and at most 1.5 percent by weight. Magnesium is added in an alloy used in accordance with the present invention as an element that increases strength. However, at higher contents, because magnesium has a negative influence on the degree of solderability in the inert gas welding process (CAB welding), the magnesium content is restricted to at most 0.3% by weight according to the present invention. If particularly critical welding processes were to be achieved, a restriction of the magnesium content to more than 0.1 percent by weight would have a favorable effect on the work result. The strength and corrosion resistance are further improved by the addition of Gr and / or Zr in the alloy used in accordance with the present invention. If the sum of the contents of Cr and Zr in the range of 0.05 to 0.4 percent by weight was maintained, this would lead to the formation of a long-lived microstructure (elongated coarse grains), in which the formation of corrosion would be impeded. intercrystalline due to the reduced grain limit surfaces. However, in combination with Mn, Fe and Ti, Cr and Zr can lead to coarse precipitations, which in turn have a negative influence on the degree of deformation and strength of the sheets produced according to the present invention. Therefore, in the alloy used according to the present invention, the content of chromium and / or zirconium is high for low contents of Mn, while it is reduced for high contents of Mn. The positive effects of Cr and / or Zr could be particularly used, reliably, if the Cr content in the melt was in the range from at least 0.1 percent by weight to at most 0.2 percent by weight and the Zr content was at more than 0.05 percent by weight. In order to avoid the negative influence of zinc on the corrosion of aluminum sheets of the type under discussion, the Zn content is restricted by 0.1 percent by weight, preferably 0.05 percent by weight. The titanium can be added in the alloy used according to the present invention for the refining of grain of the molten microstructure in contents of up to 0.1 percent by weight, preferably up to 0.05 percent by weight. In accordance with current practice, continuously melted ingots are processed from the melt as the precursor material. However, the precursor material produced in another way, obviously, could also be used as the starting material for the production of AlMn sheets according to the present invention. The method according to the present invention allows the hot rolling process to be carried out at a comparatively low preheating temperature of the metal of less than 520 ° C, which leads to a microstructure of the hot rolled strip produced, which is optimized with respect to the degree of deformation and corrosion resistance. In consideration of a good rolling capacity of the precursor material, the preheating temperature is at least 400 ° C in this case. It would be particularly favorable if the precursor material were heated to a maximum at 470 ° C and that the drying time during preheating was limited to at most 5 hours in order to maintain the largest possible proportion of Mn in solution. The manganese kept in solution is precipitated, so that it is finely dispersed during the subsequent annealing treatment (soft annealing / annealing for the second time) and in the welding process and in this way, leads to the desired high resistance, in particular, to the high values of the elastic limit Rpo.2- The starting temperature of the precursor material during the hot rolling process is preferred to be at least 400 ° C for the reasons already described. In this case, the final rolling temperature during hot rolling is above 250 ° C, preferably above 300 ° C, in order to ensure, on the one hand, a sufficient degree of deformation of the precursor material and on the other hand, the optimized formation of the microstructure during the hot rolling process. The thicknesses of the hot rolled strip are in the range of 2 to 10 millimeters. An annealing treatment is used which is carried out at the completion of the method according to the present invention for the purpose of adjusting the supply condition. The annealing treatment, in this case, could include a soft annealing or a second annealing of the cold rolled strip in the coil or in the continuous annealing furnace. If a mild annealing treatment was carried out, the temperature of the AlMn sheet during mild annealing would be at least 300 ° C, preferably at least 350 ° C. The strip treated by the annealing process is supplied from this mode to the manufacturer in the "0" state (soft annealing). In contrast, if the material were to be supplied in the malleable state, for example, in state H22 (hardened by plastic deformation, annealed a second time, with 1/4 hardness), H24 (hardened by plastic deformation, annealed by second time, with 3/4 hardness), then, the annealing treatment would be carried out as an annealing for the second time in the coil or in the continuous annealing furnace using a temperature which, consequently, will be adjusted. The common thicknesses of the finished strip of cold rolling are between 50 and 500 μ? A. For further processing of the strip produced in accordance with the present invention, it could also be favorable if the strip were coated on one or both sides using one or two Al alloys, using coating layer thicknesses of 3 to 20% of the Total thickness of the strip on each side. The alloys concerned, for example, could be common solder alloys, such as EN AW-4045, EN AW-4343, EN AW-4004, EN A -4104, and their modifications, as well as common protective coatings such as EN AW -1050, EN AW-1050A, EN A -7072, and its modifications. Preferably, the coating is applied in this case by roller coating. In the following, the invention is described in greater detail with reference to the example embodiments: In Table 1, the contents of the alloying elements are listed for AlMn sheets 1 through 8.

Table 1: Contents indicated in percentage by weight. Ingots were melted steadily from a melt having each of the corresponding compositions. This ingot precursor material was subsequently preheated to a preheat temperature which was between 400 and 520 ° C, preferably 400 to 470 ° C. The precursor material preheated in this way was hot rolled using a final temperature of hot rolled at least 250 ° C, preferably 300 ° C, up to a thickness of 3.5 mm hot rolled strip. Subsequently, the hot-rolled strip was cold-rolled in one or more passes until it reached its final thickness of 100 μm. The intermediate annealing treatment was not carried out during the cold rolling process. Finally, to adjust the supply condition, an annealing treatment was carried out, with the soft annealing or annealing for the second time being carried out in accordance with the manufacturer's instructions. Finally, the cold rolled strips were mounted in noj s. The sheets produced from AlMn in this way, in the state of supply of soft annealing, had an elastic limit limit Rpo.2 at the most of 80 MPa, a tensile strength Rm of at least 100 MPa and an elongation to the fracture A100 at least 3%. The plates that were manufactured from the sheets obtained from AlMn from 1 to 8 (NUMBER OF EXAMPLES), are intended to be used for the production of heat exchangers for automobile engines. The sheets had the ability to be cold formed using a radius of curvature of less than 1 millimeter for a 180 ° bend. After the manufacture of the heat exchangers by the welding process, each of these plates had an elastic limit Rpo.2 of at least 60 MPa, in many examples, it was greater than 65 MPa and with a variation of the resistance of corrosion. The stress tests that determine the mechanical characteristic values were made in this case with reference to the strip sections, which were subjected to a simulated welding cycle. The welding cycle was carried out, starting from the ambient temperature, using a heating speed of approximately 25 K / min. , a drying time of 3 minutes at a temperature of 600 ° C, and a subsequent cooling to room temperature using a cooling rate of approximately 40 K / min. In Table 2, the elastic limit Rpo.2 and an evaluation of the corrosion resistance for the sheets 1 to 8 in the welded state are indicated. Table 2: t) 15 = outstanding; 1 = very poor 2) 5.0 = outstanding; 1.0 = very poor It is worth mentioning that sheet 5, which contained no tin at a content of Si [% Si] of 0.84 percent by weight, had a corrosion behavior significantly worse than the behavior of the sheet 6 similarly composed, whose content of Sn [Sn%] was 0.034 percentage by weight in a content of Si [% Si] of 0.81% by weight, so that the ratio [% Sn] / [% of Si] was 0.042 in sheet 6. Sheet 8 had still better corrosion properties in the welded state, in which the ratio [% Sn] / [% Si] was 0.120. As a result of sheet 7, having a content of Si [% Si] of 0.43% by weight and without the addition of tin, a very good corrosion behavior is shown that can be achieved through low Si contents. - However, this does not lead to high values for the elastic limit Rp0.2, such as those obtained for example, in sheets 6 and 8 that have higher contents of Si. In addition, it is worth mentioning the negative influence of Cu (sheet 4) and in particular, of Zn (sheet 1) on the corrosion behavior. It is noted that in relation to this date the best method known by the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims

CLAIMS Having described the invention as above, property is claimed as contained in the following claims: 1. A method for the production of strips or sheets of AlMn, with which components are produced by the welding process, characterized in that: - a precursor material is produced from a fusion containing (in percentage by weight) Yes: from 0.3 to 1.2%, Fe: 0.5 %, Cu: 0.1%, Mn: from 1.0 to 1.8%, Mg: 0.3%, Cr + Zr: from 0.05 to 0.4%, Zn: 0.1%, Ti: 0.1%, Sn: 0.15% and unavoidable accompanying elements whose quantities Individuals are at most 0.05% and whose sum is at most 0.15%, as well as aluminum as the remainder, the precursor material is preheated to a preheat temperature of less than 520 ° C with respect to a time of dried at more than 12 hours, - the pre-heated precursor material is hot-rolled on a hot-rolled strip using a final hot-rolled temperature of at least 250 ° C, - the hot rolled strip is cold rolled on a cold rolled strip without an intermediate annealing treatment. 2 . The method according to claim 1, characterized in that the ratio of the content of Sn to the Si content of the fusion is [% Sn] / [% Si] 0. 03 3 . The method according to claim 2, characterized by the ratio [% Sn] / [% Si] is 0.1. Four . The method according to claim 2 or 3, characterized in that the Si content of the fusion is at least 0. 5 percent by weight. 5 . The method according to claim 4, characterized in that the Si content of the fusion is at least 0. 75 percent by weight. 6 The method according to any of the preceding claims, characterized in that the Si content of the fusion is at most 1. 0 percent by weight. 7 The method according to any of the preceding claims, characterized in that the Fe content of the melt is at most 0.3 percent by weight. 8 The method according to any of the preceding claims, characterized in that the Cu content of the melt is at most 0. 05 percent by weight. 9. The method according to any of the preceding claims, characterized in that the content of n of the melt is at least 1.3 percent by weight and at most 1.5 percent by weight. The method according to any of the preceding claims, characterized in that the Mg-content of the melt is at most 0.1 percent by weight. The method according to any of the preceding claims, characterized in that the Cr content of the melt is at least 0.1 percent by weight and at most 0.2 percent by weight. The method according to any of the preceding claims, characterized in that the Zr content of the melt is at most 0.05 percent by weight. The method according to any of the preceding claims, characterized in that the Zn content of the melt is at most 0.05 percent by weight. 1 . The method according to any of the preceding claims, characterized in that the Ti content of the melt is at most 0.05 percent by weight. The method according to any of the preceding claims, characterized in that the elastic limit Rpo.2 of the AlMn sheet after the welding process is at least 60 MPa, particularly at least 65 MPa. 16. The method according to any of the preceding claims, characterized in that the ingots that are continuously melted from the melt are processed as the precursor material. The method according to any of the preceding claims, characterized in that the preheating temperature of the metal is at more than 470 ° C. 18. The method according to any of the preceding claims, characterized in that the preheating temperature of the metal is at least 400 ° C. The method according to any of the preceding claims, characterized in that the drying time during the preheating is at most 5 hours. The method according to any of the preceding claims, characterized in that the thickness of the hot-rolled strip is from 2 to 10 mm. The method according to any of the preceding claims, characterized in that the final rolling temperature during the hot rolling process is at least 250 ° C, in particular, at least 300 ° C. 22. The method of according to any of the preceding claims, characterized in that the cold rolled strip is subjected to an annealing treatment. 23. The method according to claim 22, characterized in that the cold rolled strip is annealed in the coil. 24. The method according to claim 23, characterized in that the cold rolled strip is annealed in a continuous furnace. 25. The method according to claim 23 or 24, characterized in that the temperature of the AlMn sheet is at least 300 ° C during the annealing treatment. 26. The method according to claim 25, characterized in that the temperature of the AlMn sheet during the annealing treatment is at least 350 ° C. The method according to any of the preceding claims, characterized in that the thickness of the cold rolled strip is between 50 and 500 um. 28. The method according to any of the preceding claims, characterized in that the strip is coated on one or both sides using one or two Aluminum alloys, using coating layer thicknesses of 3 to 20% of the total thickness of the pull on each side. 29. The method according to claim 28, characterized in that the coatings are applied using a hot roller coating. 30. An AlMn strip or sheet for producing components by welding, characterized in that it is produced according to a method according to one of claims 1 to 29.